Abstract:

Bromoxynil herbicide resistance in oilseed rape ('Brassica napus ' L.) is conferred by transgenic insertion of a single gene from a soil bacterium that confers the ability to metabolize hydroxybenzonitrile herbicides such as bromoxynil. The level of resistance of bromoxynil herbicide is high but it is unknown whether there is a biological cost associ ted with this resistance gene or the derived herbicide resistance in oilseed rape. The performance of two isogenic transgenic bromoxynil resistant populations, Westar 235 and Westar 237, and one transgenic bromoxynil resistant line, 235 245 derived from Westar were evaluated. All were either sprayed with bromoxynil at 280 g a.i./ha or left unsprayed and were compared to the nontransgenic population, Westar. The bromoxynil resistance gene can be used as a very accurate and definitive marker to measure unidirectional pollen mediated gene flow (outcrossing) in oilseed rape because it is inherited as a single, nuclear, dominant gene. Unidirectional outcrossing rates were assessed between neighbouring plots and rows of oilseed rape in a typical plant breeding field situation, specifically, a plot to plot trial, a row to row trial (40, 80, and 120 cm row spacings), and a plot to plant trial. (Abstract shortened by UMI.)